The Big Walker Mountain Tunnel is a vehicular tunnel in the Appalachian Mountains ofSouthwest Virginia that carries Interstate 77 through/under Big Walker Mountain. It is located at 37°2.316′N 81°7.818′W, a few miles south of the town of Bland and a segment of the Appalachian Trail, and about 20 miles (32 km) south of its longer cousin, the East River Mountain Tunnel.

The 4,229-foot (1,288 m) tunnel was first opened in 1972 after five years of construction labor. It carried a price tag of $50 million, which at the time was the most expensive single project undertaken on Virginia's interstate system. The opening of the tunnel reduced the travel time from Wytheville to Bland County by 30 minutes.

Preliminary engineering studies for the project were made by Brokenborough & Watkins, consulting engineers of Richmond, Virginia, and the final design of the roadway and tunnel was by Singstad & Kehart, consulting engineers of New York City.